Network applications employ network protocols for communication between a network client and a network server. Network protocols can be classified into two main categories: connectionless protocols; and connection-oriented protocols. A connectionless protocol is an asynchronous protocol without a persistent connection between the network client and the network server. For example, a web browser client communicates with a web server using a connectionless protocol known as the hypertext transport protocol (HTTP). Using HTTP, the web browser client can make requests of the web server, such as a request for a particular web page. The web server receives each request as a distinct request which is independent of all other requests, and responds to each request independently. A connection exists between the web browser client and the web server for only as long as it takes to send a request and receive a response. Thus, there is no persistent connection between the web browser client and the web server for multiple requests and responses, and HTTP is therefore considered to be a connectionless protocol.
In contrast, a connection-oriented protocol provides a persistent connection for the transmission of data between a network client and a network server. Connection-oriented protocols also usually include facilities for error, sequence and flow control. Error control refers to a combination of error detection, correction and acknowledgement sufficient to compensate for any unreliability inherent to the network. Sequence control ensures that the network client and the network server are able to reconstruct data received over the network in the proper order in which they were intended to be received, and is essential in the transmission of large volumes of data. Flow control ensures that network clients and network servers do not overrun each other with too much data. An example of a connection-oriented protocol is the transmission control protocol (TCP) which provides these facilities. An application of TCP is video streaming over a network where a streaming video client can create a persistent connection with a streaming video server for the receipt of streaming video data using TCP. The TCP connection is used by the streaming video server to send large streams of video data for receipt by the streaming video client. Other applications of connection-oriented communications include mobile telephone connections to cellular base stations, digital set-top box connections to a digital television service provider and connections between network chat clients such as Lotus Sametime Connect (Lotus is a registered trade mark of International Business Machines Corp.) and AOL Instant Messenger (a registered trade mark of America Online Inc).
Connection-oriented protocols offer effective and reliable communication between network clients and network servers, and support applications requiring long lived connections or connections over which large quantities of data can be transferred A technique for creating a connection-oriented connection between a network client and a network server is outlined below. A network server will include a server configuration comprising one or more  server parameters. Similarly, a network client will include a client  configuration comprising one or more client parameters. For example, in a streaming video application, a streaming video server may include a server configuration with a video frame rate parameter corresponding to the frame rate of video data streamed from the server. Similarly, a streaming video client may include a client configuration with a maximum frame rate parameter corresponding to a maximum frame rate of video data the client is able to receive. A network client requests a new connection to a network server using the connection-oriented protocol. This can involve an initial message being sent from the network client to the network server with an indication that a new connection is requested. The network server responds to the initial message with a connection acceptance message, including details of the network server configuration. The network client receives the network server configuration and determines if the client configuration is compatible with the server configuration. For example, the server configuration may include a frame rate which exceeds a maximum frame rate of the client configuration, and the network server configuration is therefore incompatible with the network client configuration. If the client configuration is compatible with the server configuration, a connection is created between the network client and the network server. If the client configuration is not compatible with the server configuration, the network client may abandon the request to create a connection.
A server configuration can also be changed during a connection-oriented Network connection, and such a change can affect connected network clients. For example, one or more connected network clients may be incompatible with a new server configuration, such as a new value of a frame rate parameter of a streaming video server. When a server configuration is changed, the network server must determine a course of action for connected network clients. One technique for changing a server configuration involves disconnecting all connected network clients before the server configuration is changed. Network clients are then able to reconnect and determine if the client configuration is compatible with the new server configuration. This technique has the disadvantage that connected network clients which are compatible with a new server configuration are disconnected unnecessarily, and the quality of service provided by the network client is consequently reduced. An alternative technique for changing a server configuration involves only introducing a new server configuration for new connections. Existing connections continue to operate under the original server configuration (i.e. prior to a change to the configuration). This alternative technique has the advantage that existing connected network clients are not disconnected. However, this alternative technique has the disadvantage that the server must Support both an original server configuration for existing connected network clients, and a new server configuration for new network client connections. This can increase the processing requirements of the network server and reduce the performance of the network server. Furthermore, existing connected network clients which support the new server configuration continue to communicate with the server using the original server configuration. This is a particular disadvantage where the new server configuration offers advantages over the original configuration which are to the benefit of existing connected network clients (such as an increase in communications speed).
It would be desirable to provide a way to change a server configuration of a network server with connected network clients without disconnecting the connected network clients which are compatible with the changed server configuration, and without the need for the network server to support multiple server configurations.